The present invention relates to an H bridge circuit, and more particularly, to a new gate drive method for an H bridge circuit.
An H bridge circuit is a type of circuit that is well known to those the skilled in the art. If there is no Schottky diode in the H bridge circuit, the current through the inductor can induce the turn-on of both the body diode and the parasitic NPN device during dead time.
FIG. 1 is a schematic diagram showing a cross-section of a conventional isolated NMOS device. The minority carrier injection and power dissipation will happen when there is a large current in the parasitic NPN device.
In the prior art, the gate drive voltage is 0 and there is no current assignment between the NMOS device and the parasitic NPN device during the dead time. Injection of a substrate minority carrier can induce a function error and performance degradation of the circuit. The large current in the parasitic NPN device can sometimes greatly increase the power dissipation and other potential issues, such as self-heating effects, reliability, and so on.
It would be advantageous to have an H bridge circuit that is not susceptible to the above described problems.